High-frequency induction furnace



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G. F. HARRINGTON ET AL HIGH FREQUENCY INDUCTION FURNACE Filed June 1; 1927 2 Sheets$heet l WITNESSES: o

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' ATTORNEY Nov. '13, 1928. 1,691,349 I G. F, HARRINGTON ET AL HIGH FREQUENCY INDUCTION FURNACE Filed Jurie 1, 1927 2-Sheets-Sheet 2 II II INA! I I III/ I [M s 1.\\w q wk n, A

WITNESSES: INVENTORS deoryeF/farrmy/an} ATTORNEY Patented Nov. 13,1928.

UNITED STATES PATENT OFFICE.

GEORGE I. HARRINGTON, OF EDGEWOOD; AND PORTER H. BRACE, OF WILKINSBURG,

PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC 8! MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

HIGH-JI'REQ'U'ENCY INDUCTION FURNACE.

Application filed Iuni 1,

Our invention relates to heat treating furnaces and more particularly to heat treating furnaces of the induction type.

An object of our invention is to provide an induction furnace for heat treating a plurality of articlesof uniform size which are passed 'therethrough in a contmuous stream at a predetermined rate of speed.

Another object of our invention is to provide a mechanism for discharging heat treated articles from a furnace at a predetermined rate, which means serves also to prevent the influx of air into the furnace chamber during the discharging operation.

Another object of our invention is to provide means for preventing condensation of moisture driven out of the heated'articles at the cold or charging end of the furnace.

In practicing our invention we provide an elongated vertically disposed graphite tube or muffle with an inductor coil surrounding the central portion thereof'to efi'ect inductive heating of the mufile and of material passed therethrough, A plurality of articles, which in the present instance are of disc shape, are stacked within the mufile, and a motor-actuated means effects the removal thereof, one at a time, from the bottom of the stack. Upon the removal of each article, the stack remaining in the muffle is lowered by gravity 1 to permit the removal of the next article. A

second inductor. coilof relatively few turns isprovided at the upper-end of the muflle to preheat said articles and. maintain sufficient temperature thereat to prevent condensation of the moisture driven out of. the articles during the heating operation.

In the drawings,

Figure 1 is a view, in ve f'tical section, of a furnace embodying our invention,

Fig. 2 is a plan view of a detail of the discharge mechanism, I

Fig. 3 is'a viewin section on the line III III of Fig. 2,

Fig. I is a development in section on line I.V-IV of Fig. 2, and

Fig. 5 is a fragmentary view in vertical section of a modified form of discharge mechanism.

50 The furnace embodying our invention comprises a casing formed of three Superposed sections, each section comprisin an annular shell 2 of suitable refractory eatinsulating material set in grooves in annular casing.

192?. Serial in. 195,629.

refractory plates 4. A grooved metallic an nular ring 5 is. seated upon the upper peripheral edge of the top section 2, and a similar ring 5 is seated upon the lower peripheral edge of the lower section 2. The top of the upper section is closed by a cast metallic cap 6 resting upon the ring 5 which'is provided with an annular passage 8 to permit the circulation of a cooling fluid therethrough. A similar cap 10 closes the bottom of the lower section, in face-to-face relation with the lower ring 5, and is provided with an annular passage 12 for the circulation of a cooling fluid. Pipes 14-44. and 1515 conduct the cooling fluid into and out of the passages in the upper and lower caps respectively. 1

The caps 6, rings 5, sections 2, and plates 4 are secured in assembled relation by a plurality of rods 16, the ends of which are screw-threaded and project through apertures formed in rings 5 and caps 6 and 10 to be engaged by nuts 17.

The caps 6 and 10 are apertured centrally thereof to permit the passage therethrough of a graphite tube or muffle 20, comprising a plurality of interfitting sections, which extends the entire length of the casing. The bore of tube is slightly enlarged at the upper end thereof to accommodate a tube 22, of nichrome, or other suitable material, for a purpose hereinafter described. A plate 24 with an aperturein the center thereof adapted to register wit-h the bore of tube 20, is bolted to the lower face of the casting l0 and supports the tube in position within the The plate 24 is provided with a chamber 26 and pipes 2828 to permit the circulation of a cooling fluid therethrough.

A plate 30, having an annular depending flange 32, caps the upper end of tube 20 and projects a short distance into the aperture in plate 6, and is resiliently clamped-to the cap 6 by means 01 bolts and compression springs 34,35, so that the sections of tube 20 are always forced togetherirrespective of the relative expansion and contraction of the tube and casing, and the tube is securely held in the casing.

The plate 30 is axially apertured and -flanged at 36 to register with the bore of tube readily movable cover- 40 encloses the extendefined by flange 36 and an annular flange 42. Regulation of the flow of cooling fluid through the caps 6 and 10, or the omission of cooling means altogether, will effect desired changes in the temperature gradient through which the articles pass during the heat treating operation.

Within the upper section of the furnace casing and surrounding tube 20 is a hollow inductor coil 44 of a relatively small number of turns. Terminals 45, 46 thereof extend .through shell 2 for connection with a suitable source of electric power and a cooling fluid supply. L y

In the center section of the casing is an inductor coil 48 comprising a helix of flattened tubing with terminals 49, 50 extending through the shell 2 to provide for connection with a source of electric power and a cooling fluid supply.

Thermal insulation consisting of a finely divided refractory, such as zirconium silicate, fillsthe entire casing and the space between the inductor coils and the graphite tube 20.

Supporting legs 51 are secured, at the upper ends thereof to the casting 10, and at their lower ends to a suitable base 52.

The discharge mechanism comprises a wa ter cooled casting 60 secured to the lower face of plate 24 and provided with a circular recess in the face thereof adjacent to plate 24. A discharge passage 62 extends from said circular recess through the casting 60 into communication with a suitable receptacle 64. A circular disc 66 substantially fills said circular recess and is mounted for rotation upon an'axis mid-way between the axes of the bore of tube 20 and of the openof the disc 66 is effected by means of a shaft 68 keyed thereto which extends downwardly through a stuffing box 70 with the lower' end thereof received 1n.a suitable bearing 72. A worm gear 74 is keyed to shaft 68 and motion is imparted thereto through suitable reduction gearing 76, 78, driven by an ele tric motor. 80.

The plate 66 shown more particularly in Fig. 2, is provided with a plurality of peripherally spaced apertures 82 of substantially the same diameter as the bore of tube 20 and so arranged that upon rotation of plate 66, the apertures will be moved to register with the bore of tube 20 and the opening ofdischarge chute 62 successively. With particular reference to thedeveloped section of plate 66 as shown inFig. 4,-it will be noted that the surface of the plate is gradually inclined downwardly at 67 toward the apertures 82 and the portion of the late at the opposite side of the aperture is slightly chamfered as at 69.

In the present embodiment, the furnace is designed for the heat treatment of disc shaped objects which are inserted inthe uppaer end of tube 20 to form a stack therein.

otation of. plate 66 in a clockwise direction will bring one of the apertures 82 into registration withthe bore of tube 20, thereby permitting one of the discsto be received therein and causing a consequent lowering of the stack. In effecting this result the disc at the bottom of the stack is gradually lowered byunovement of the inclined surface 67 of plate 66 so that abru t dropping of the stack is avoided. Furtfier rotation of plate 66 brings the portion 69 thereof into engagement with the bottom disc thereby removing itfrom the stack, and continued rotation brings the disc into registration with the opening of discharge passage 62 and permits it to drop therein.

The slightly chamfered edge 69 of plate 66 permits operation of the device with discs varying considerably in thickness, the only requirement being that the disc be at least as thick as the vertical surface of the portion 69, and not greater in thickness than the thickness of plate 66. It is clearly within the scope of the present invention, however, to so proportion the thickness of plate 66 with a respect to the thickness of the discs, that the discharge of two or more of the discs at a time is possible."

The rotation of plate 66 is continuous at any desired speed depending upon the time necessary for the proper heat treatment of the discs within the tube 20. s

A plate 71 of suitable heat resistance material is fixedly mounted in the circular recess in the casting 60 beneath plate 66 to effect a snug fit between the plate and castings 24 and 60 so that the entrance of air into tube 20 is substantially prevented. To insure a more complete exclusion of air, an air-tight cover (not shown) may be provided for the receptacle 64.

A tube 100 extends through the intermediate section of the furnace casing 2 into communication with the heated section of the tube or muflie 20, to accommodate a thermocouple or other appropriate means for determining the temperature of the heated zoneof the mufile.

In Fig. 5 we have shown a modified form of discharge mechanism comprising an apertured plate 90 reciprocated by means of a connecting rod 92 and a crank disc 93 actuated by an electric motor 94. The reciprocation of the plate 90 successively brings it into registration with the bore 95, containing a stack of heated discs and the opening of a discharge chute 96, whereby the discs are removed one at a time from the bottom of the stack and dropped into the discharge chute.

In operation, the tube 20 is filled with a stack, of discs to be heated and inductor coils 44 and 48 are electrically connected to a .suitable source of alternating current.

The purpose of coil 44 is ,td maintain the temperature of the upper end-of tube 20 at a value sufiicient to prevent condensation thereon of moisture driven out of. t e heated discs, and to preheat the discs as t ey are substantially uniform in size.

inserted into the tube.

the inner wall of tube 20 and to avoid this difiiculty we have provided tube 22 of a suitable heat and moisture resistant mate rial, such as nichrome, which lines the upper portion of the bore.

Energization of motor 80 rotates plate 66 and as the apertures 82 therein register with the bore of tube 20 the bottom disc ofthe stack is received therein and is carried,

upon continued rotation, into registration with the discharge chute 62. Upon the removal of each disc, the discs remaining in the stack are lowered by gravity so that the movement of the discs through the tube is substantially continuous and the speed thereof may be readily controlled through motor .80. Additional discs may be added to "the top of the stack'in the tube 20, either by manual orby automatic means, as; may be desired, so that the heat treating process is continuous.

It is obviously within the scope of our invention to modify the structure shown to heat treat articles of various shapes, the only requirement being that the articles be The .mufile 20 may beprovided with a plurality of bores for increased production, and may be foi med of various materials 'to effect desired chemical or thermal results. Also, the circulation of gases through the muffle to effect desired chemical action orto remove moisture driven out of the discs, may be resorted to and accomplished by extending a conduit, such as 102, permitting the passage of. such gas; through the furnace casing into communication with the bore of ber, thereby effecting the constant movement of the articles through the chamber and the substantial exclusion of air therefrom.

Various modifications may be made inour A small percentage -.of the moisture, however, tends to corro e invention without departing from-the spirit and scope thereof, and We desire therefore. that only'such limitations! shall be placed thereon as are imposed by the prior art and the appended claims.

We claim as our invention:

1. An induction furnace for heat treating a continuous train of articles of uniform size, comprising a vertically disposed elongated graphite tube adapted to contain a stack of said articles, an. inductor coil surrounding the central portion of said tube to effect the heating thereof, and asecond inductor coil of relatively few turns surrounding the upper end'of said tube to effect a desired temperature gradient longitudinally of said tube. i

2. In a heat treating furnace, the combination with a tubular muffle and an inductor coil for heating an intermediate portion only of said mufllc, of an auxiliary inductor coil for heating the receiving end of said mutlie to prevent the condensation therein of moisture driven out of the articles being heat treated, and a moisture resistant lining for said muflie at the receiving end.

1 3. In a heat'treatiug furnace, the combination with a'tubular mufiie, an inductor coil for effecting heatin of an intermediate portion only of the mu e, and a casing surrounding the mufile and coil, of closure members at the respective "ends of the casing for holding the tubular muille in proper operative position in said casing, and fluid cooling means in said closure members for ensuring a predetermined sequence of temperaturevalues in said muflle longitudinally thereof. g

4. In aheat treating furnace, the combination with a mufilecomprising a plurality of coaxial interfitting tubular portions, and electric means for heatin an intermediate portion only of the mu e to a relatively 105 high temperature, of an auxiliary electric means forheating the inlet end of the mufiie to a lower temperature than that of the intermediate'portion, a casing surrounding the muffle and the several heatingmeans, fluid cooled end members associated with the case ing for closingthe ends thereof and for holding the muffle therein, and. resilient means associated with one of said end members for effecting close engagement ofthe interfitting portions of the muflie under all conditionsof operation of the furnace.

In testimony whereof, we have hereunto subscribed our names this 9th day of May, 1927, and this26th day of May, 1927, re- 120 spectively.

GEORGE F. HARRINGTON. PORTER H. BRACE. 

